Rack ovens are generally equipped with a fuel-fed heating element and a fan for moving heated air throughout a baking chamber to provide a rapid distribution of hot air over the food product. Commercial ovens of this type include a baking chamber, which is sized to receive a rack having multiple shelves containing products to be baked; a power driven, rotating mechanism to rotate the product as it is being cooked or baked; a heat exchanger including one or more gas burners and an exhaust system to eliminate combustion gases; and a circulating system for directing hot air along a heated air flow path that passes through the baking chamber. Conventional rack ovens of the type for baking bread also generally include a steam generator for the introduction of steam into the oven for brief periods of time, usually at the beginning of the baking process, to impart a desired color and crispness to the crust of the bread.
In convection ovens such as that described in U.S. Pat. No. 5,617,839, a rack oven includes a heat exchanger comprising a plurality of heat exchange tubes, and a plurality of gas fired in-shot burners, wherein each of the in-shot burners fires into a corresponding heat exchange tube. One or more blowers circulate air past the heat exchange tubes and to the oven baking chamber. The input openings of the plurality of heat exchange tubes are arranged in a plurality of horizontal rows, each row containing a plurality of input openings, the rows spaced vertically from each other. Each tube then extends across an air flow region into a vertical gas collection duct, with corresponding tubes then extending back across the air flow region to another gas collection duct and so on. It is also known to eliminate the gas collection ducts by simply providing heat exchange tubes having appropriate bends. These arrangements present a relatively large lateral footprint for the heat exchanger, which impacts the necessary width for the overall oven.
In-shot burner type heat exchangers can also exhibit a phenomenon called “candling” when the gas supply to the manifold is initially turned off. Candling is defined as residual gas burning at the gas manifold orifices.
FIGS. 24A, 24B and 24C illustrate another PRIOR ART rack oven construction 300 in which a heat exchanger section 302 is positioned alongside the baking chamber 304. The wall 306 separating the baking chamber 304 from the heat exchanger section 302 includes a single, centrally disposed opening 308 having an axial fan 309 positioned therein. The wall 306 also includes louvers 310 towards the sides thereof The heat exchanger section 302 includes a plurality of horizontally extending, U-shaped exchange tubes 312, with tube segments 320 and 322, are arranged vertically one above the other. When the fan 309 is rotated, air flows from the baking chamber 304, through the opening 308 onto a central section of the heat exchange tubes and then splits in two lateral directions along the heat exchange tubes to be returned to the baking chamber via louvers 310 as best seen by the arrows in FIG. 24A. As best reflected in FIG. 24B, there is also a substantial vertical (upward and downward) component to the air flow in the heat exchanger section 302 due the central location of the opening 308. Likewise, there would be a significant vertical component to the air flow in the baking chamber 304 as well. A steam generator (not shown) is also provided in the prior art oven 300. As best seen in FIG. 24C, the U-shaped heat exchange tubes 312 are arranged at progressively increasing angles to the horizontal when moving away (either upward or downward) from a vertically central location 324 of the tubes.
Typical rack ovens also commonly include baking chamber floor constructions that include a non-insulated single floor panel that is anchored to the floor on which the oven sits and/or is rigidly, non-adjustably connected to the side walls of the oven. Because rack ovens should be level upon installation and site floors are not always level, anchoring the baking chamber floor to the site floor and/or rigidly fixing the baking chamber floor to the oven side walls does not facilitate movement of the oven from one location to another. Further, anchored floors may experience buckling due to thermal expansion. This floor construction can also be used on non-gas burning versions of ovens, such as electric versions.